IO-Uring Archive on lore.kernel.org
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From: Pavel Begunkov <asml.silence@gmail.com>
To: Jens Axboe <axboe@kernel.dk>,
	io-uring@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: Tejun Heo <tj@kernel.org>, Dennis Zhou <dennis@kernel.org>,
	Christoph Lameter <cl@linux.com>
Subject: [PATCH v2 2/3] io_uring: batch getting pcpu references
Date: Sat, 21 Dec 2019 19:15:08 +0300
Message-ID: <229f00564ac243cee0bfef8372a8581efedc0da2.1576944502.git.asml.silence@gmail.com> (raw)
In-Reply-To: <cover.1576944502.git.asml.silence@gmail.com>

percpu_ref_tryget() has its own overhead. Instead getting a reference
for each request, grab a bunch once per io_submit_sqes().

basic benchmark with submit and wait 128 non-linked nops showed ~5%
performance gain. (7044 KIOPS vs 7423)

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 513f1922ce6a..5392134f042f 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1045,9 +1045,6 @@ static struct io_kiocb *io_get_req(struct io_ring_ctx *ctx,
 	gfp_t gfp = GFP_KERNEL | __GFP_NOWARN;
 	struct io_kiocb *req;
 
-	if (!percpu_ref_tryget(&ctx->refs))
-		return NULL;
-
 	if (!state) {
 		req = kmem_cache_alloc(req_cachep, gfp);
 		if (unlikely(!req))
@@ -4391,6 +4388,7 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr,
 	struct io_submit_state state, *statep = NULL;
 	struct io_kiocb *link = NULL;
 	int i, submitted = 0;
+	unsigned int extra_refs;
 	bool mm_fault = false;
 
 	/* if we have a backlog and couldn't flush it all, return BUSY */
@@ -4400,6 +4398,10 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr,
 			return -EBUSY;
 	}
 
+	if (!percpu_ref_tryget_many(&ctx->refs, nr))
+		return -EAGAIN;
+	extra_refs = nr;
+
 	if (nr > IO_PLUG_THRESHOLD) {
 		io_submit_state_start(&state, nr);
 		statep = &state;
@@ -4415,6 +4417,7 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr,
 				submitted = -EAGAIN;
 			break;
 		}
+		--extra_refs;
 		if (!io_get_sqring(ctx, req, &sqe)) {
 			__io_free_req(req);
 			break;
@@ -4451,6 +4454,8 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr,
 		io_queue_link_head(link);
 	if (statep)
 		io_submit_state_end(&state);
+	if (extra_refs)
+		percpu_ref_put_many(&ctx->refs, extra_refs);
 
 	 /* Commit SQ ring head once we've consumed and submitted all SQEs */
 	io_commit_sqring(ctx);
-- 
2.24.0


  parent reply index

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-17 22:28 [PATCH 0/2] optimise ctx's refs grabbing in io_uring Pavel Begunkov
2019-12-17 22:28 ` [PATCH 1/2] pcpu_ref: add percpu_ref_tryget_many() Pavel Begunkov
2019-12-17 23:42   ` Jens Axboe
2019-12-18 16:26     ` Tejun Heo
2019-12-18 17:49       ` Dennis Zhou
2019-12-21 15:36         ` Pavel Begunkov
2019-12-17 22:28 ` [PATCH 2/2] io_uring: batch getting pcpu references Pavel Begunkov
2019-12-17 23:21   ` Jens Axboe
2019-12-17 23:31     ` Jens Axboe
2019-12-18  9:25       ` Pavel Begunkov
2019-12-18  9:23     ` Pavel Begunkov
2019-12-18  0:02   ` Jens Axboe
2019-12-18 10:41     ` Pavel Begunkov
2019-12-21 16:15   ` [PATCH v2 0/3] optimise ctx's refs grabbing in io_uring Pavel Begunkov
2019-12-21 16:15     ` [PATCH v2 1/3] pcpu_ref: add percpu_ref_tryget_many() Pavel Begunkov
2019-12-21 16:15     ` Pavel Begunkov [this message]
2019-12-21 16:15     ` [PATCH RFC v2 3/3] io_uring: batch get(ctx->ref) across submits Pavel Begunkov
2019-12-21 16:20       ` Pavel Begunkov
2019-12-21 16:38         ` Jens Axboe
2019-12-21 16:48           ` Pavel Begunkov
2019-12-21 17:01             ` Jens Axboe
2019-12-21 17:26               ` Pavel Begunkov
2019-12-21 20:12       ` [PATCH v3 0/2] optimise ctx's refs grabbing in io_uring Pavel Begunkov
2019-12-21 20:12         ` [PATCH v3 1/2] pcpu_ref: add percpu_ref_tryget_many() Pavel Begunkov
2019-12-21 20:12         ` [PATCH v3 2/2] io_uring: batch getting pcpu references Pavel Begunkov
2019-12-21 21:56           ` Pavel Begunkov
2019-12-28 11:13         ` [PATCH v4 0/2] optimise ctx's refs grabbing in io_uring Pavel Begunkov
2019-12-28 11:13           ` [PATCH v4 1/2] pcpu_ref: add percpu_ref_tryget_many() Pavel Begunkov
2019-12-28 11:13           ` [PATCH v4 2/2] io_uring: batch getting pcpu references Pavel Begunkov
2019-12-28 11:15             ` Pavel Begunkov
2019-12-28 17:03               ` Jens Axboe
2019-12-28 18:37                 ` Pavel Begunkov
2019-12-30  3:33                   ` Brian Gianforcaro
2019-12-30 18:45                     ` Pavel Begunkov

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